Manufacture of isopropyl ether



Jan. I8-, 1938. R. ROSEN ET AL 2,105,508

MANUFACTURE OF' ISOPROPYL ETHER Filed Dec. 29, 1934 C'A TCH TA NK PFOPYLENE l' 433 ORP TIO/V TOWR ,4c D J opac-:E 20 'mi COOLER 7% LYNN-w OIL 0 0 TL ET SODA' .ScSRL/BBER.

ORJTEAH /NLLT HEA TEK ETHER GE/VAT//VG W5- w 9m.

isopropyl and other ethers.

Patented Jan. 18, 1938 PATENT carica MANUFACTUBE 0F ISOPROPYL ETHER Raphael Rosen, Cranford. Hyym E. Bac, Roselle, and Robert B. Lebo, Elizabeth, N. J., assignors to Standard Alcohol Company Application December 29,199.4. serial No. 159,660

4Claims.

This invention relates 'to a. process of manufacturing isopropyl ether direct from propylene.

According to the prior art, .ethers are generally manufactured fromthe corresponding alcohols. 'For instance, olenes are contacted with concentrated, e. g. 90-95%.. sulfuric acid to form monoalkyl sulfates which are then ,hydrolyzed with water to form the alcohols. These, in turn,

are contacted with strong sulfuric acid and two molecules of the alcohol are condensed with the splitting oil of water to form one `molecule of the ether. Such a process has been practiced both for manufacturing ethyl ether asA well as The present invention is a simplified process in which propylene is converted directly into isopropyl ether by contactingA it with sulfuric acid of substantially one concentration, preferably between the approximate limits of and 85%.

Several methods of carrying out Ithe invention may be used, i. e.:

One method comprises mere contacting of the propylene with sulfuric acid of about concentration under optimum temperature and pressure conditions, such as 50 to 100 lbs. pressure and a temperature between the approximate limits of 75 and 125 C. Such a process may be conveniently carried out by passing the popylene gas upward through a tower pked with inert contact bodies, such as Raschig rings, and trickling the sulfuric acid downwardly from the top in countercurrent to the. rising propylene gas. 'The vapors issuing from the top are then condensed and fractionated to obtain the ether, and the acid issuing from the bottom of the tower is recycled to the top. This same process may be carried out by feeding the propylene in through a. porous thimble at the bottom of a tower filled with acid and drawing on ether-containing va.- pors at the top.

Another method comprises absorbing the propylene at a low temperature, e. g. 0 to 50 C.

. (preferably about 20 C. to 30 C. in 'I5-85% 0 preferably about 200 lbs. when H3804), and driving of the ether at high temperature, e. g. 100 to 125 C., this being conveniently done in a tall tower. cooled at the bottom and heated at the top, in which the pre ure may be the same throughout, el g. 50lto 500ylbs., y the absorption is carried out at about 20 C. i

A third method comprises carrying out the ab- A sorption and ether generation in two separate vessels maintained at the same temperture but underv diierent pressures, for example, absorbing under a pressure of 50 to 500 lbs. per square inch and at a temperature of 100 to 125 C. and taking oil. the ether-containing vapors by releasing the pressure to about atmospheric.

A fourthmethod is the same as the third ex- ,alent isopropyl alcohol.

moved from the absorption zone and sufficient cept that different temperatures are used. In other words, two separate vessels are used for absorption and ether conversion, the temperature and pressure both being different in these two vessels. kFor instance, the absorption may be conveniently carried out under a pressure of about 200 lbs. per square inch (roughly 50 to 500 lbs.) and at a temperature of 20 C. (roughly 0 vto 50'C.), using sulfuric acid of about 80% concentration and the ether generation being carried out at about atmospheric pressure and at a temperature between the approximate limits of 100 and 125 C.

Another example of this preferred method of operation is to .absorb propylene in to 85% sulfuric acid at 200 lbs. pressure and 25 to 35 C. where an acid product is obtained containing 10 lbs. of 86 sulfuric acid per gallon of equiv- This product is rewater is added to bring the acid strength below 80% (to prevent polymer formation during the' generation of ether), preferably near '75%. The product is then heated to to 110 C. and the mixture 'of isopropyl ether, isopropyl alcohol and propylene generated is fractionated to separate these three materials.

The accompanying drawing is a. schematic layout of apparatus suitable for carrying out this method.

It is preferred to carry out the invention in a continuous manner (although a batch process may be used) and accordingly it isgenerally desirableto add make-up water (or steam) in order to compensate for the amount of water withdrawn from the acid by converting the propylene into isopropyl ether according to the reaction:

2c31a+H2o c3Hvoc3H7, x and any water withdrawn in the fractionating zone. Other economies and efiiciencies are obtained by recycling oleiines (which may be generated along with the ether) to the absorption zone, also by recycling "any isopropyl alcohol (which may be generated along with the ether) to ythe ether generation zone, and also by the useof heat exchangers between the raw materials and products of the absorption and ether generation zones. Any polymers which may be formed in the absorption zone may either be ref moved, cracked and recycled to the absorption zone, or may be passed on through the ether generation zone and fractionated to a desired boiling point, for instance, to make a product suitable for blending with motor fuels.

Referring to the drawing, propylene gas from any desired source, not shown, is fed through line l through catch tank 2 into the bottom of absorption tower 3 in countercurrent to sulfuric acid which is fed through line I into the top of line I 5 into the original feed line I.

tower 3. Unabsorbed gases, consisting chiey of saturated hydrocarbons which may have been present in the feed gas containing the propylene, pass oil.' at the top of the tower 3 through line 5.

,The sulfuric cid descending in the tower 3 becomes c arged with absorbed propylene ,and passes via line 6 through .heat` exchanger 1 and steam heater 8, then via line into ethergenerating pots Illwhich may be heated by steam or any other suitable means, the vapors driven oi! then passing through `soda scrubber II into fractionating column I2, from which any propylene or other gases liberated are passed through scrubber I3, compressor I4, and recycled through vapors condensing at the top of the fractionating column I2 are withdrawn through line I6 and cooler Ilia from the top plate oi? the fractionating column I2. f (f 'I'he liquor Withdrawn at the bottom of the fractionating column I2 consists chiey of isopropyl alcohol (liberated as a by-product in the ether generating pot) together with about 30% of water, and is, with or without removal of the water, conveniently refiuxed through line I1 into ether generating pots I0, or Withdrawn at I'Ia for further rening as alcohol. The reuxing of the alcohol to theether generating pots permits more accurate control of-conditions under which the ether is generated andl also permits the acid to be concentrated to a higher fstrength before running to the absorption zone. The spent acid liquor issuing from these. ether generating pots I0 is' recycled through line I8, through heat exchanger 1, cooler Il, into the acid storage tank 20, from which it is withdrawn by means of pump 2l to be fed through line 4 back into the top of absorption tower 3. Any polymerized oil forming in the propylene absorption tower 3 may be withdrawn from the bottom of tower 3. Makel up water or steam, required to compensate for thefwater withdrawn from the acid by conversion' of propylene into isopropyl ether, may. be added to the acid liquor passing from absorption y' tower 3 to ether generating pot I0. A mixed ether 1 may be made by feeding ethyl alcohol from line .6a into line 3.

Instead of using pure propylene, commercially available gases containing appreciable amounts of 'propylene may be used; for instance, the stabilizer gas from liquid phase cracking contains up to 1.0% propylene and from vapor phase cracldng, D to 30% or more. The propane fraction of fractionated gyro gas or vvapor phase yerackingmay contain as high as 60 to 70% propylene. 'Ihe propylene or gases containing same, may be puried in any desired manner before beingjcontacted with the sulfuric acid; for in- "itreated with stance.. they may be scrubbed with soda or triethanolamine, ete. to remove sulfur.'

The absorption obthepropylene in the sulfurie acid may be aided by adding to the ,acid a small amount of isopropyl ether or of a higher molecular weight' ether. This step may be con-- lvenfently carriedout by recycling into the ap' propriate point of the absorption zone a small acid in one vessel and then this charged liquor is passed into an ether generating vessel, which may be heated by steam for instance, the vapors issuing from this generator are preferably scrubbed with soda in order to remove any free acidwhich may be carried over mechanically in the vapors, the scrubbed vapors then being fractlpnated in a suitable fractionating column, if desired, to separate the isopropyl ether from some isopropyl alcohol which may have been formed simultaneously. However, it may not always be necessary or desirable to separate this small amount of isopropyl alcohol from the isopropyl ether as a small amount of this alcohol will not do lany harm when the ether is to be used as a motor fuel or motor` fuel blendingagent and, in

fact, a small amount of this alcohol may be considered to be a valuable addition agent.

The invention has beenfound particularly applicable as a commercial method of making isopropyl ether for use as a. motor fuel or motor fuel blending agent, which subject matter has been disclosed and claimed in co-pending application Serial No. 648,211, filed December 21, 1932 by Hyym E. Buc.

The invention is not to be limited to the speciflc embodiments shown or the specic examples given, nor to any theories advanced as to the operation of the invention, but in the appended claims it is intendedto claim all inherent novelty in theinvention as broadly as the prior art permits.

We claim: l

1. Then process of manufacturng isopropyl ether which comprises 'absorbing propylene in sulfuric acid of about 70 to /85%,concentration at a temperature between the approximate limits Vof 0 and 50 C. and under a pressure of aplproximately 50 to 500 lbs. per square inch maintaining the sulfuric acid at the said concentration of approximately 70 to 85% and then ger.- erating isopropyl ether fromY said acid at a temperature of about 100 to 125C. at approximately atmospheric pressure.

2. Process of manufacturing isopropyl ether, which comprises converting propylene directly into ether by contacting lt with a hydrating catalytic medium at a temperature between the approximate limitsof 0 and 50 C. and under a `pressure of 'approximately 50 to 500 pounds per square inch whereby a substantial amount of ether is formed which remains in solution in .the hydrating' catalytic medium, after which said Vhydrating,catalytic medium is subjected to heat to remove the said ether from solution;

.3. Process of manufacturing isopropyl 'ether according to claim `2, in which Vthe hydrating catalytic medium ismaintained at the same coneentrationl and used continuously to form the said ethers.

- i. Process of manufacturing isopropyl ether, which comprises absorbing propylene in sulfuric acid of about .'10 to 85%ooncentration at a temperature and under a pressure to keep isopropylv .ether in solution 'in the sulfuric acid as it is formed, andthen separating the isopropyl ether ,fromv the saidsulfuric acid at a higher temperature and lower. pressure so that ether may be separateds a vapor. I Y RAPHAEL ROSEN.

HYYM E. BUC.

ROBERT B. LEBO. 

